Nabataean Cement

“Cement mortar and plaster played an important role in Nabataean life. They used this essential technology from their very earliest years in the desert. Without their special knowledge of cement, the Nabataeans would never have conquered the desert, and would never have risen to the status of a civilization.

Other tribes in the deserts of Arabia lived within the limits that nature put on them. They stayed close to sources of water, and ranged their sheep and camels from there. The Nabataeans on the other hand, built water channels and cisterns far out in the desert to collect the scant rainfall and store it for their use.

Without this knowledge of waterproof cement, the Nabataeans would not have become the far ranging merchants of the Middle East, who easily traversed deserts and inhospitable, barren mountains.

As long ago as 50 BC Diodorus Siculus wrote in his book Bibliotheca Historica about the Nabataeans, “They are conspicuously lovers of freedom and flee into the desert, using this as a stronghold. They fill cisterns and caves with rainwater, making them flush with the rest of the land. They leave signals there which are known to themselves and not understood by anyone else. They water their herds every third day, so that they do not constantly need water in waterless regions, if they have to flee.” The information that Diodorus gathered was already common knowledge in the Middle East. The Nabataeans had been building hidden water cisterns for years.

As with the Romans, the Nabataeans secret to waterproof cement was the material known as pozzolan. Where the Romans used volcanic ash to create their waterproof cement, the Nabataeans had a much easier source. In the Hisma desert near Wadi Rumm are major surface deposits of silica, which geologists today claim is nearly 100% silicon.

B. Mason, in his book Principles of Geochemistry provides a technical discussion of research into geology to explain rock composition. For instance, he explains how a pozzolan material can be created by ground water seeping through silica. While the Romans had to search for this key component of ancient waterproof concrete, the Nabataeans simply had to locate places where water had seeped through the silica and scoop it up and add it to their lime plaster.”

Read the rest of the article at the source: Nabataea.net

Bacillus pasteuri, naturally occurring bacteria, can be used to turn sand into sandstone (calcite cement). This relatively simple process creates durable, low cost building materials. The technical name for this is microbial-induced calcite precipitation (MICP). Ginger Krieg Dosier of the United Arab Emerites was awarded the Metropolis 2010 Next Generation Winner for her innovative work. “If Dosier’s biomanufactured masonry replaced each new brick on the planet, it would reduce carbon-dioxide emissions by at least 800 million tons a year. Don’t bake the brick – grow it.”

From the above article: “Here are 12 simple steps for reproducing Dosier’s competition-winning idea. 1. Place the formwork in the sand. 2. Fill it up. 3. Level. 4. Shake the bacteria solution. 5. Pour it over the sand. 6. Let it saturate. 7. Pour the cementing solution over the sand. 8. Let it saturate. 9. Watch the brick harden. 10. Remove the formwork. 11. Watch the brick harden some more. 12. Behold, an ecobrick!”

Magnus Larsson: Turning Dunes into Architecture

Magnus Larsson: Turning Dunes into Architecture

Magnus Larsson, an architecture student who’s researching applications for MICP explains his proposed 6,000 kilometer habitable wall across Africa using bacteria-solidified sand in this TED talk.

Benefits of MICP stabilized earthbags include:
– stronger, more earthquake and hurricane resistant structures
– possibly thinner walls
– more durable water-resistant walls
– less tamping/faster construction
– less use of cement

Hurdles remain, however. The process gives off ammonia and so Dosier continues her research.

Magnus Larsson dune architecture

Magnus Larsson dune architecture

Image credit Magnus Larsson
The Better Brick: 2010 Next Generation Winner
Bio-Soil Improvement Their research involves stabilizing soils under the foundation.
Magnus Larsson.com
Big thanks to Scott Howard of Earthen Hand for alerting me to this concept.

Ultra-High Performance Concrete

Ultra-High Performance Concrete

“According to a recent article in the Economist, Iran happens to be good, very good, at developing what is known as “ultra-high performance concrete” (UHPC). Because of its geographical position, the county is under constant threat of earthquakes. The most devastating earthquake in recent memory occurred in the city of Bam, located in southern Iran, and claimed the lives of 30,000 people. As a result, Iranian engineers have developed – out of necessity – some of the toughest and most rigid building materials in the world.

So how does Iranian concrete standout? Well, unlike conventional concrete, Iranian concrete is mixed with quartz powder and special fibers – transforming it into high performance concrete that can withstand higher pressure with increased rigidity. What this all translates to is excellent building material given the environment that has found peaceful applications like the construction of safer bridges, dams, tunnels, increasing the strength of sewage pipes, and even absorbing pollution.”

Read the full article at the source: Digital Trends.com

Construction Details and Evaluation of an Experimental Kiln
“In 1996 ITDG (now Practical Action) commissioned Paragon Ceramics Ltd to build an experimental lime kiln at Dedza in Malawi. Paragon designed the kiln in partnership with local lime burners. It works with a variety of fuels and can be operated as a batch or continuous production kiln. Where wood is the only fuel option, the kiln works well burning softwood which could be grown on a managed plantation. Good quality hydrated lime and lime putty have been
produced for building. These notes are a practical guide on how to build the kiln, and explain its operation. Because it is experimental the Dedza kiln is small. Anyone who wishes to build a bigger kiln should seek further advice.”

Read the full PDF at the source: Shelter Centre.org

Concrete is the most common building material in the world and its use has been increasing during the last century as the need for construction projects has escalated. Traditionally, concrete uses Ordinary Portland Cement (OPC) as binder, water as the activator of cement and aggregate. Finding an appropriate replacement for traditional concrete is a desirable solution to obviate the environmental problems caused by cement production. The use of fly ash as a partial replacement for Portland cement is a method to maintain the properties of concrete and reduce the need for cement. Fly ash is a by-product from coal-fired power plants and is abundantly available. The percentage of cement replacement can be varied according to application and mix design. One of the potential materials to substitute for conventional concrete is geopolymer concrete (introduced by Davidovits in 1979). Geopolymer concrete is an inorganic alumino-silicate polymer synthesized from predominantly silicon, aluminum and byproduct materials such as fly ash. Geopolymer properties have been investigated for several years and it is still a major area of interest among researchers and industry partners as it does not contain cement and uses fly ash and alkali liquids as binders to produce a paste to consolidate aggregates. Furthermore, the aggregate comprises a substantial portion of concrete. Including coarse and fine aggregates it is normally obtained from natural sources. Fine aggregate in Australia is usually mined from sand quarries. As the demand for concrete production increases, more natural sand is needed. The need for fine aggregate should be addressed in an environmentally friendly manner, considering the diminishing sources of natural sand. Red sand is a by-product generated from the manufacture of alumina from bauxite by the Bayer process.

Previous studies on properties of red sand have shown that it has the potential to be used in concrete as a fine aggregate. While the use of red sand in traditional concrete has been investigated by some researchers, no research has been reported regarding the use of this by-product in manufacturing geopolymer concrete. This research looks into the replacement of natural sand fine aggregates with red sand in geopolymer concrete. Initially, an extensive series of mixtures was prepared and tested. The objective of the research was to identify the salient parameters affecting the properties of geopolymer concrete when natural sand is replaced by red sand. At the next stage, attempts were made to enhance the mechanical and durability features of red sand geopolymer concrete. The final stage consisted of testing red sand geopolymer concrete to find out the various properties of this novel construction material.

Source: Espace Library at Curtin.edu

Easy Chanvre hemp block building system

Easy Chanvre hemp block building system

To meet 21st century environmental, economic, and social constraints, the construction sector has to focus on new materials that meet:
* climate demands (fighting CO2 releases),
* saving of fossil fuel resources,
* use of renewable raw materials,
* conservation of water resources,
* respect for biodiversity.

Use of these ecomaterials allows:
Reduced costs of use,
Creation of new jobs,
Waste-free job site management,
A healthy habitat (air quality, water).
Blocks and slabs made of hemp concrete are molded industrially and dried naturally in our factory.

Source: Easy Chanvre

Geopolymers – Alkali Activated Composites for Encapsulation of Intermediate Level Wastes

Geopolymers – Alkali Activated Composites for Encapsulation of Intermediate Level Wastes

Source: Immobilization Science Laboratory

“Geopolymer cements offer an alternative to, and potential replacement for, ordinary Portland cement (OPC). Geopolymer technology also has the potential to reduce global greenhouse emissions caused by OPC production. There is already a considerable amount of work and research conducted on geopolymers in the past decades, and it is now possible to implement this technology commercially. However, to ensure that geopolymer becomes commercially available and able to be used in the world, further understanding of its ability to provide durable and long lasting materials is required. One main property which is still relatively unexplored compared to other properties is its shrinkage properties. The objective of this thesis is therefore to examine the shrinkage of geopolymers and factors which might influence it.

The factors which influence geopolymer strength were investigated as being the factors which may influence shrinkage. The selection of the activating solution is an important factor in forming the final product of a geopolymer. Activating solution SiO2/Na2O ratio is determined to be an important influence on the shrinkage of geopolymer. SEM images of the samples enable observation of the sample topology and microstructure. An important observation was the existence of a ‘knee point’ which also occurs in OPC shrinkage. The ‘knee point’ is the point where the shrinkage goes from rapid shrinkage to slow shrinkage. From SEMs it is noted that the samples past the knee point are shown to have a smoother topology which means it is more reacted.”

Source: Melbourne University Library

Floating Cities

I prefer low tech, low cost approaches, but it’s fun to consider larger scale solutions and what could happen in the future.

This paper presents the findings of an experimental investigation to study the effect of alkali content in geopolymer mortar specimens exposed to sulphuric acid. Geopolymer mortar specimens were manufactured from Class F fly ash by activation with a mixture of sodium hydroxide and sodium silicate solution containing 5% to 8% Na2O. Durability of specimens were assessed by immersing them in 10% sulphuric acid solution and periodically monitoring surface deterioration and depth of dealkalization, changes in weight and residual compressive strength over a period of 24 weeks. Microstructural changes in the specimens were studied with Scanning electron microscopy (SEM) and EDAX. Alkali content in the activator solution significantly affects the durability of fly ash based geopolymer mortars in sulphuric acid. Specimens manufactured with higher alkali content performed better than those manufactured with lower alkali content. After 24 weeks in sulphuric acid, specimen with 8% alkali still recorded a residual strength as high as 55%.

Source: Waset.org